<option value='' ><?php echo $this->translate('select course ..')?></option>
<?php foreach($this->data as $subjectName=>$val): ?>
<optgroup label="<?php echo $subjectName?>">
<?php foreach($val as $sn=>$groupName):?>
<option value="<?php echo $sn?>"><?php echo $groupName?></option>
<?php endforeach;?>
</optgroup>
<?php endforeach;?>